Exposure to solvents is widespread, both in certain occupations and in the general environment. There is a strong need for data quantifying cancer risks for suspected and known carcinogens, including trichcloroethylene (TCE) and benzene, particularly for cancer sites that are less well-described or for which the association is controversial. There are studies suggesting that these and other solvents may increase the risk of multiple myeloma (MM); however, individual, regionally-based epidemiologic studies of MM have been severely limited by the disease's rarity, hindering the ability to describe these associations with confidence. Much larger numbers are needed to study occupational solvent exposures, particularly to characterize risks across varying exposure intensity levels or with increasing duration. With an efficient approach of combining existing MM epidemiologic data resources for collaborative reanalyses, we will pool data from 13 case-control studies participating in the International Multiple Myeloma Consortium (IMMC) to conduct the most powerful study to date of risks associated with occupational solvent exposures. Completed studies participating in the IMMC include over 3600 cases and 12,000 controls with questionnaire data on occupation (e.g., job title/industry with- or without additional questions on tasks and exposures), and based on these data we will assess exposure to five specific solvents of particular interest: trichloroethylene (TCE), perchloroethylene (PCE), benzene, toluene, and xylene. Family history of lymphohematopoietic cancers is also important to harmonize across IMMC studies as it is a likely risk factor for MM and therefore a critical factor to consider as a potential confounder or effect modifier (as an indicator of inherited susceptibiliy to develop MM) of occupational or other exposures. For example, we will explore interactions between occupational solvent exposures and family history of these cancers in development of MM, an interaction that has been suggested for non-Hodgkin lymphoma, and which may indicate an interaction between genetic variants and solvent exposure in lymphoma etiology. The IMMC is the best (and perhaps the only) current setting to address our study aims, not only because of the study size, but because the participating case-control studies collected occupational and family histories with a level of detail that isn't matched in typical cohort studis. Our effort in coding and harmonizing variables across participating studies will develop a valuable resource for future consortium studies of other occupational exposures, genetic variants associated with familial- versus non- familial MM, and gene-environment interactions.